arm/arm64: KVM: Ensure memslots are within KVM_PHYS_SIZE

commit c3058d5da2222629bc2223c488a4512b59bb4baf upstream.

When creating or moving a memslot, make sure the IPA space is within the
addressable range of the guest.  Otherwise, user space can create too
large a memslot and KVM would try to access potentially unallocated page
table entries when inserting entries in the Stage-2 page tables.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
[ luis: backported to 3.16: used shannon's backport for 3.14 ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index 0258b22bf9d1a6e3a3e5c970d955374b1c24f4c3..2555a52cccd2cea7459cb09e5b67212bf5600283 100644 (file)
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -926,6 +926,9 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run)
 
        memslot = gfn_to_memslot(vcpu->kvm, gfn);
 
+       /* Userspace should not be able to register out-of-bounds IPAs */
+       VM_BUG_ON(fault_ipa >= KVM_PHYS_SIZE);
+
        ret = user_mem_abort(vcpu, fault_ipa, memslot, fault_status);
        if (ret == 0)
                ret = 1;
@@ -1150,6 +1153,14 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
                                   struct kvm_userspace_memory_region *mem,
                                   enum kvm_mr_change change)
 {
+       /*
+        * Prevent userspace from creating a memory region outside of the IPA
+        * space addressable by the KVM guest IPA space.
+        */
+       if (memslot->base_gfn + memslot->npages >=
+           (KVM_PHYS_SIZE >> PAGE_SHIFT))
+               return -EFAULT;
+
        return 0;
 }